Participants in this research study at the Clinical Research Center (CRC) at the Oregon Health Sciences University will be patients who have been diagnosed with Cushing's Disease. The purpose of this study is to measure hormones that may be abnormal in patients with Cushing's Disease. Cortisol, an adrenal gland hormone, is increased in Cushing's Disease. Cortisol is also increased in stress, and it can be difficult to distinguish between Cushing's Disease and stress. We hope that a hormone called corticotropin releasing hormone (CRH) is suppressed in Cushing's Disease, but increased in stress. The study will involve one admission to the CRC that will last 7 days.